Vegetable oils are typically oils that have been pressed or extracted, such as from a vegetable source. Many vegetable oils contain some form of phosphatides (e.g., hydratable or non-hydratable), commonly known as gums. For instance, soybean oil contains about 1-3%, corn oil 0.6-0.9%, sunflower oil 0.5-0.9%, and canola oil (crude) 1-3% of gums.
Gums can be partially or totally removed from vegetable oils through several different known degumming processes, as described below. The most commonly used processes in the industry are water degumming, acid degumming, caustic refining and enzymatic degumming, for example, as disclosed in U.S. Pat. Nos. 4,049,686; 5,239,096; 5,264,367; 5,286,886; 6,001,640; 6,033,706; 7,494,676 and 7,544,820; and U.S. Pat. Pub. Nos. 2007/0134777; 2008/0182322 and 2012/0258017.
A method disclosed in U.S. Pat. No. 4,240,972 discloses adding an acid to a heated stream of crude vegetable oil. The oil stream is passed through a static mixer to produce an acid-in-oil dispersion having acid droplets and then the dispersion is separated into an oil phase and an aqueous phase containing the phosphatides. The static mixers for use in the process are commercially available under the trade-names Kenics Static Mixer, Komax Motionless Mixer, Series 50 In-Line Blender by Lightnin, Ross Motionless Mixers and Sulzer Static Mixer. These devices are tubular structures having fixed, mixing elements inside, which accomplish flow division and radial mixing, simultaneously. The static-mixer is sized to give a flow velocity of about 3 m/sec to 7.6 m/sec.
U.S. Pat. Nos. 4,698,185 and 6,0159,15 describe processes for degumming vegetable oil using a high shear Ultra-Turax rotor/stator apparatus. Similarly, U.S. Pat. No. 6,172,248 describes improved methods for refining vegetable oils and byproducts thereof. In an organic acid refining process, vegetable oil is combined with a dilute aqueous organic acid solution and subjected to high shear to finely disperse the acid solution in the oil.
U.S. Pat. No. 8,491,856 describes a system for stripping fatty acids from triglycerides containing a high shear device with a rotor, and wherein the rotor is rotated at a tip speed of at least 22.9 m/s (4,500 ft/min) during formation of the dispersion.
In yet another example, up to 99% phospholipids can be removed from soybean oil by an ultrasonic reactor (Moulton, K. J., Mounts, T. L., “Continuous ultrasonic degumming of crude soybean oil,” Journal of the American Oil Chemists' Society, 67, 1990, 33-38).
A method disclosed in U.S. Pat. Application No. 2009/0314688; 2011/0003370 and 2014/0087042 involves mixing crude oil with degumming agents, i.e., water or acid, and passing the mixture through a hydrodynamic cavitation device. Numerous flow-through hydrodynamic apparatuses are known, for example, U.S. Pat. Nos. 5,810,052; 5,971,601; 5,969,207; 6,035,897; 6,502,979; 6,705,396; 7,338,551 and 7,207,712. Cavitational processing of oils provides high shear to the degumming process, but such processing suffers from extracting dissolved gases from liquids by generating post cavitation gas fields of tiny bubbles in the oil flow. Those bubbles result in a flotation process for the soap stock particles and can entrap oil in the larger agglomerates, which can increase oil yield losses.
Accordingly, there is a continuing need for reactor for degumming, which can provide high shear to the process and eliminate undesirable degassing problems.